Met and Yankee fans by the thousands are set to descend on Bryant Park this afternoon for a raucous rally – a day before they scream their lungs out at the first game of the Subway Series.

Emotions are running high.

So much so that 200 cops will separate Met and Yankee boosters at the rally.

“There’s no question that the city of New York and whole metropolitan area is gripped by baseball fever,” Mayor Giuliani said with uncharacteristic understatement at City Hall.

Urging fans to declare their allegiance to one team or the other, the mayor held up a hat with combined Met and Yankee logos “for the faint of heart.”

Then the city’s No. 1 Yankee fan donned his Bombers cap.

Met pitcher Al Leiter was on hand with his 5-year-old daughter, Lindsay, and to no one’s surprise, he put on a Met cap.

When the Amazin’s won the pennant, Leiter poured champagne on Giuliani’s head in the team’s locker room.

“It’s my hope I get to pour champagne on your head one more time,” chortled the hurler.

The first Battle of the Boroughs since 1956 gets under way tomorrow night at Yankee Stadium.

Billy Joel will sing the National Anthem, while Don Larsen and Yogi Berra, batterymates for Larsen’s historic 1956 World Series perfect game, will team up again for the first-pitch ceremony.

At Bryant Park yesterday, Amazin’s fans were saying bring on the Bombers.

“The Yanks are old and tired and it’s time for the new, revitalized Mets to take them out. They’ll win in six,” predicted Peter Silverman, 23, a paralegal from Howard Beach, Queens.

The Flushing Favorites in six was also the prediction of Scott Snyderman, 37, a Manhattan Internet consultant.

“We match up as well as the Yanks. Pitching is better, especially in the bullpen. Bring them on, we’re ready,” he said.

Steven Clement, 44, of The Bronx, a Bryant Park worker, said the Mets will do it in four.

“Forget about the Yankees. The Mets are the best, they are the champs. The Yankees can’t touch the Mets. They never have and they never will.” he said.

Yank fans, of course, disagreed.

“History tells you the Yanks are going to win. I’ve been a fan since I was 9 and I like their chances,” said Jim Sommers, 54, of Los Angeles.

Stephen Romandetto, 39, a Manhattan computer consultant, agreed.

“The Yanks have always been the dynasty and the Mets have always been scrappy. I was born on the day Roger Maris hit his 41st home run [in the course of Maris’ then-record-setting 61] in 1961, and I’ve been a fan since,” he said.

Mel Cash, 42, a delivery guy from Brooklyn, put it more bluntly.

“The Yanks have more experience and I think they’re gonna bust the Mets’ ass,” he said.

In a tradition as old as the Subway Series, rival fans will face off before the rally begins in a Nathan’s Famous hot-dog eating contest – in its first revival in 44 years.

The wiener emporium says such a face-stuffing slugfest has predicted the Subway Series winner with remarkable accuracy – in fact, nine out of 13 times.

To make sure civil war doesn’t break out between Met and Yankee fans at the games, 950 cops will be at Yankee and Shea stadiums for the games – 400 more than during the home teams’ home playoff games.

In addition, in each police precinct around the city, a sergeant and eight cops will be assigned to patrol sports bars.

Police sources said the NYPD has not received intelligence reports of any planned terrorist attack.

But they said the department is aware of the problems in the Mideast and must be aware of a possible attack – and prepared if one happens.